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Homework Help: Head of a vector

  1. Sep 28, 2003 #1
    The question asked me to find the head of a vector [a,b,c] whose length is 3 and is in the same direction as vector
    a=[-3,-4,12]

    So I found the follwing:

    Let vector x be the unknown vector

    |a|=13
    |x|=3

    Since they are both in the same direction, they both must have the same direction angles right?

    So:

    Cos alpha = -3/13 which is equal to a/3
    Cos beta = -4/13 which is equal to b/3
    Cos gamma = 12/13 which is equal to c/3

    Then I got the values for a,b and c but the book shows me a different answer. What am I doing wrong here?
     
  2. jcsd
  3. Sep 28, 2003 #2

    Hurkyl

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    What values did you get, and what does the book say?
     
  4. Sep 28, 2003 #3
    I found my answer to be correct because I did a similiar question and found my method to work. Thx though
     
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